Postage stamps are a unique type of document in that the purchaser buys a one-time service to have a hard-copy document delivered by the postal service that issued the stamp. Counterfeiting of stamps presents a challenge to the counterfeiter because the value per document is comparatively low compared to other targets such as currency or bearer bonds. Large postal services can, however, be considered an attractive target due to the high volume of stamps produced, particularly for letter format mail. The US market, for instance, can have billions of stamps in a single series that are used primarily on letters. At a price of $0.44 and 10 billion per year issued a 2% rate of counterfeiting represents a $88,000,000 loss per year. Because the post must deliver the mail with the counterfeit stamp this is more than foregone revenue; it is a true bottom line loss.
When stamps are distributed by the post itself through local post offices, the distribution is well controlled and the opportunity for a counterfeiter to introduce large volumes of fake stamps is extremely limited. In some cases, the post may use a distribution network that is not tightly controlled such as stores, rental centers, etc. This gives an organized counterfeiter the opportunity to introduce high volumes of fake stamps. An example would be a chain of rental centers whose owner is in collusion with a counterfeiter. The fake stamps could be introduced and the sales kept “off the books” generating a profit nearing the face value of the stamps.
Luminescence detection has been used by the U.S. Postal Service (USPS) for the detection and orientation of stamps on mail pieces. The USPS has relied upon luminescence detection for almost 45 years to identify stamp authenticity and to orient letters processed by automatic sorting machines. This technique of tagging stamps with phosphorescent material was developed in the Netherlands in the late 1940s and early 1950s. A machine based on the Netherlands' design was purchased by the USPS as its first facer canceller. A later upgrade known as the Mark II facer canceller became the workhorse of the stamp cancellation process and remained in service for over 25 years. Its replacement, the advanced facer canceller system (AFCS) has boosted performance even more, but still uses the luminescence detection process to orient and determine where to cancel each mail piece.
In 1963, stamps tagged with phosphorescent ink were introduced to work with the facer canceller machine technology. Originally, two types of phosphorescence tagging were used: green taggants for First Class mail, and red taggants for airmail. Only the green is currently used. Postage meter manufacturers were encouraged to add phosphorescent inks to their products. The highly abrasive nature of the phosphorescent compounds shortened the life of the metering mechanisms and the meter manufacturers objected to this proposal. Work was done to develop fluorescent inks with non-particulate dyes that would fluoresce under the ultraviolet illumination of the detectors. These inks were introduced in the early 1970s.
The choice of phosphorescence for stamps and fluorescence for meters yielded another benefit. Phosphorescent inks continue to glow after the excitation illumination is turned off, but fluorescent dyes do not. The detection systems could take advantage of this property to discriminate between stamps and metered indicia. This technology has remained a cornerstone of facer canceller design to this day. In order to assure consistent quality of the stamps and meter marks, special purpose instrumentation was developed to measure the quantitative signal obtained when the stamp or indicium was exposed to specific wavelengths of ultraviolet light. The USPS “2C” meter has filled that role for about 30 years. Recently high quality counterfeit stamps have begun to appear in the mail. Such stamps are routinely reintroduced into the mainstream even if rejected for no phosphor at the facing and canceling equipment. The USPS at present makes no systematic effort to prevent counterfeit stamps and permit marks from passing through the mail stream.
When phosphorescent inks were first added to stamps, all of the printing was done exclusively by the Bureau of Engraving and Printing, Department of the Treasury. Over the past decade or two, the printing of stamps has been outsourced to multiple commercial printers. This has resulted in healthy competition and reduced printing costs with advanced technology and better equipment. It has also resulted in more complex quality control and inspection procedures and processes. Because there are only a limited number of 2C meters, the strain on maintaining quality is becoming a logistical issue.
Tagging stamps has proven to be reliable and cost effective, but it results in a process that cannot differentiate between types of stamps nor their values. High detection rates may be achieved, but not without some problems. For example, either stamps are tagged, or they are not; that is, stamps with a value of ten cents or higher are normally tagged, while lower denomination stamps are not. Since unused stamps have no expiration date and a stamp could be applied to a letter many years after its date of issue, it is possible to cancel older tagged stamps on mailpieces that do not contain sufficient postage. In contrast, a quantity of untagged stamps can be applied to an envelope to meet the revenue requirements, but be rejected by the detection system. From a philatelic perspective, this is common when stamp collections are broken up into valued and unvalued portions; the unvalued stamps are then used for postage. Other examples of tagging problems are low phosphorescent signals resulting from stamps that have been mistakenly run through the washing machine or from stamp designs with dark colors printed over pre-coated phosphorescent paper without the application of additional phosphorescent ink.
The Postal Inspection Service has long relied upon the phosphorescence in stamps to aid in determining whether stamps are counterfeit. Phosphorescent inks are not readily available and require offset or other commercial printing equipment for application. A common counterfeiting method is to digitize the image of a stamp and then print stamps with ink jet printers. These printers use dye-based inks that result in stamps that look very similar when viewed under normal lighting. However, under shortwave ultraviolet light they can be quickly identified as counterfeit.
Technology has advanced and a new method of stamp detection has been developed and is about to be deployed by the USPS. Siemens has developed a high-resolution color imaging camera system to identify stamps, metered indicia, and bar code patterns based on the information in the pattern. This Advanced Color Recognizer 2050 (ACR2050) is scheduled for deployment with the new Advanced Facer Canceller System (AFCS200). The present invention seeks to take advantage of this development.